1. Field of the Invention
This invention relates to ramjet fuels.
2. Description of the Prior Art
A high performance ramjet engine commonly referred to as the Modern Ramjet Engine has recently been devoloped for use in military applications. Specifications dealing with the properties of fuels to be used in this engine are more stringent than those for fuels used in older, lower performance engines. Among the specifications are requirements that the fuel have a volumetric heat of combustion in excess of 154,000 B.T.U./gal., a viscosity of less than 177 centipoises at -40.degree. C and a flash point of greater than 60.degree. C. Previously used fuels do not meet these stringent requirements. For example, pure hydrogenated norbornadiene dimer (also known as Shelldyne H and RJ-5) meets the heating requirement but is several times too viscous at -40.degree. C. As other examples, RJ-4 and JP-5, which are well known to be excellent low viscosity fuels, meet the viscosity requirements but are far too low in volumetric heat of combustion to be useful in the Modern Ramjet Engine.
Because previously used fuels were unsuitable for one reason or another, considerable experimentation was carried out. In particular, combinations of hydrogenated norbornadiene dimer, which was known to have a suitable volumetric heat of combustion with various other materials were experimented with in attempts to find a combination having a suitable balance among volumetric heat of combustion, viscosity and flash point. Combinations of hydrogenated norbornadiene dimer with decalin, with TH-dimer, with toluene, with benzene and with many other materials all failed to meet specifications for one reason or another.